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Update: With few hard frosts, tropical mangroves push north

Posted onDecember 31, 2013

A newly established black mangrove grows amid salt marsh plants north of St. Augustine, Florida, near the northern limit of this cold-sensitive tropical tree’s range. Mangroves are expanding into North Florida as killing frosts become rare there. Credit: Kyle C. Cavanaugh

Cold-sensitive mangrove forests have expanded dramatically along Florida’s Atlantic Coast as the frequency of killing frosts has declined, according to a new study based on 28 years of satellite data from the University of Maryland and the Smithsonian Environmental Research Center in Edgewater, Maryland.

Between 1984 and 2011, the Florida Atlantic coast from the Miami area northward gained more than 3,000 acres (1,240 hectares) of mangroves. All the increase occurred north of Palm Beach County. Between Cape Canaveral National Seashore and Saint Augustine, mangroves doubled in area. Meanwhile between the study’s first five years and its last five years, nearby Daytona Beach recorded 1.4 fewer days per year when temperatures fell below 28.4 degrees Fahrenheit (-4 degrees Celsius). The number of killing frosts in southern Florida was unchanged.

The mangroves’ march up the coast as far north as St. Augustine, Florida is a striking example of one way climate change’s impacts show up in nature. Rising temperatures lead to new patterns of extreme weather, which in turn cause major changes in plant communities, say the study’s authors.